It is known to use a tongue manipulation device to treat upper airway obstruction and sleep disordered breathing.
Respiratory disorders during sleep are recognized as a common problem with significant clinical consequences. Obstructive Sleep Apnoea (OSA) causes an intermittent cessation of airflow. When these obstructive episodes occur, an affected person will transiently arouse. Because these arousal episodes typically occur 10 to 60 times per night, sleep fragmentation occurs which produces excessive daytime sleepiness. Some patients with OSA experience over 100 transient arousal episodes per hour. OSA may also lead to cardiovascular and pulmonary disease.
Various approaches are known which aim to maintain the airway passage during sleep. Oral appliances aimed at changing the position of the soft palate, jaw or tongue are available, but patient discomfort has limited their use. Continuous Positive Airway Pressure (CPAP) devices are often used as first-line treatments for OSA. These devices use a sealed mask which produces airflow at a slightly elevated pressure and acts to maintain positive air pressure within the airway.
This invention relates to an approach by which a tongue manipulation device is surgically applied to a patient. Aspire Medical was the originator of the “Advance” implantable tongue suspension technology.
The technology is described in detail in US2008/0023012 for example, on which FIGS. 1 to 3 are based.
The complete device comprises three essential parts:    (i) a tissue anchor which is surgically placed inside the tongue;    (ii) a bone anchor which is typically attached to the mandible; and    (iii) a tether line which fixes the tissue anchor to the bone anchor.
The bone anchor comprises a spool, enabling the surgeon to spool the tether into the bone anchor. This process is called titration and advances the tongue in the direction of the mandible (or prevents the tongue moving back), preventing blocking of the airway. The spool arrangement comprises an indexing part and a spool part, so that an audible sound is made during titration so that the degree of tightening can be judged. The indexing part can also retain the spool in a fixed position after adjustment or a separate lock can be used. The spool has a fixed number of stable positions over one spool revolution. Clockwise turning (for example) provides spooling up the tether line, and counter clockwise turning provides unspooling. The optimal advancement can be found by spooling back and forth.
Clinical studies have shown that the “Advance” technology is able to significantly reduce the number of apnoeic events in moderate and severe apnoea patients.
One possible issue with the known designs is that with the spool position held by the indexing mechanism (i.e. in the absence of a separate mechanical locking device) unspooling of the tether can arise over time, if the indexing part fails. The indexing part can for example have an indexer spring that forces the spool to take one of the stable positions (for example there may be six such positions). If the indexing part fails through reduced spring stiffness, the holding torque is lost, leading to unspooling of the tether. Each titration step loads the springs which step by step can degrade the holding function.
Another disadvantage of the known system is that it is difficult to feel whether the tether is tight or not as each indexed rotation requires a minimum torque to overcome the indexer springs. Thus, the user does not have a feel for the tether line tightness.